Power lift for tractors



March 24, 1953 E.- v. BUNTING 2,632,628

' POWER LIFT FOR TRAC-I'ORS Filed Nov. 25, 1946 4 Sheets-Sheet 2 IN VEN TOR. ERNEST V BUN TING Byz 5, MM/

ATTO NEYS March 24, 1953 E. v. BUNTlNG 2,632,628

' POWER LIFT FOR TRACTORS Filed Nov. 25, 1946 4 Shetg-Sheet s INVENTOR. ERNEST M BUN TING A T TORNEYS March 24, 1953 E. v. BUNTING 2,632,628

' POWER LIFT FOR TRACTORS Filed Nov. 25, 1946 4 Sheets-Sheet 4 w'- INVENTOK 05 ERNEST v. HUNT/N6 Fay-1 "44.4", r

ATTORNEYS,

Patented Mar. 24, 1953 POWER; LIFT FOR TRACTORS Ernest V. Bunting, Dearborn, Mich., assignor to Harry Fergusomlno Detroit, Mich, a, COI'DO! r n o Dela are ApplicationNovembcrZS, 1946, SerialNo. 712,125,

21; C aims... (01. 254-113) The. present inven ion h s o d wit power lift devices for tract rs.- uoh d i es are eneral, used for h manipulation of v us implements and the like which may be attached to the tractor.

\Qne general object of the invention is to provide an improved follow-up type of control such that the implement or ot load will he rais d or lowered by the lift d ce to l w W h fidelity the movement i a han contr o er o similar device,

M re particularly, it is zen-o jec to r vid such a control usin a power lift w h p ston and cylinder type actuator and in which provision is made for effect n a correc e va iat i the volume of fluid beh nd the piston to r tain the piston automatically and at al im s n a osi' tion relative to th cylind whi h orr sp nds to the position of a manual control lever or the like in. th latte fs an of movem n Approaching the matter in asomewhat different aspect, it is an objsct of the invention to control automat ll he operation of a tracto borne power lift device strict response to han in t e. ited. po it n of the l ad and n a manner to retain the same correctively in a preset position and irrespective of changes in the magnitude ,of the load.

Mechanism embodying the present invention may either be incorporated as a part of the initial tractor structure, .or arranged as a conversion mechan m .f a p ic ti n to exist n tra s having a load-responsive type of automatic lift control such as that shown in Henry George Ferguson Patent No. 24118 180, issued May 2 1938. Because so many tractors equipped with the latter control s ste ar h w i us the provision of a conversion mechanism for direct application to them is of primary practical importanoe. It is an ob e t o h P se in ention to provide such a conversion mechanism,

quire, and which is of low cost, rugged construction and substantially foolproof in operation.

A further object of the invention is to pro.-

vide a power lift arrangement for tractors with a control set-up such that the same may be readily conditioned alternatively for operation either as a position-responsive system, or as a power lift devices together with a coasting crane. arrangement such that any given control move ment of the manual control lever or the like for the system is translated into a corresponding proportional increment of vertical movement for the outer active end of the crane boom or the like.

Another object is to provide new and improved crane mechanism for operation with tractor borne vertically swinging lift means which are actuated by a hydraulic ram, which mechanism embodies means for translating any unit move.- ment of the ram throughout its range into subs. stantially a proportional .unit movement of the free end of the crane so that the available lift.- ing force at that point will be uniform through: out the range of crane movement.

A further object is to provide a crane attache ment for tractors equipped with power operated draft links and which embodies a liplgagc arrangement such as to impart a substantially true vertical motion to the active outer end of the crane boom, despite the generally arcua-te inot of th oute end o the supporting .d ait which the attachment is carried,

Further objects and advantages of; the invert:

Fi 22 is a side aera n o th a p atus shown.

in Fig, 1 the near rear wheel of the tractor h g re o d an certain porti ns o the t ct r ho ll me bein b ok n away to indicate th locati or interiorly located parts. a t

g, 3 is a Vi w similar to Fig. 2, but sn t the crane in elevated, rat n lowgredl, pol-r sition. 4 a s Fig. 4 is an enlal'gfid detail side elevation a cam and cam follower arrangement {included in the apparatus of Figs. 1 to :3 and 1utiliz d if o riapi-l plying thrust to valve control rod on thetractor. Fig. 5 is a rear elevation v of the apparatus shown mFigalandZ. 1 views, on enlargedscale, of an upper link bly included in the apparatus of gi 'ig- Figs. 6 and 7 are, respectively, side and p13 la .8 s a d ail d transverse sectional iow ok su tant lly along the line 11;; .5

Fig. 9 is a view similar to Fig. 3, but showing a modified form of of control apparatus embodying the present invention.

Fig. 10 is an enlarged detail sectional view taken substantially along the line Ill-48 in Fig. 9.

Fig. 11 is an enlarged detail plan view of a thrust applicator included in the installation of Fig. 9 and with certain parts in section looking in the direction indicated by the line HIl in Fig. 9.

Fig. 12 is an enlarged detail View taken substantially along the line l2-l2 in Fig. 11 and showing in side elevation the connection at the forward end of the thrust link.

As heretofore noted, the present invention contemplates the possible provision of a conversion mechanism that may be applied to existing tractors equipped with load-responsive automatic controls for a power lift. Accordingly the invention has been here illustrated as embodied in a construction such that a portion of the apparatus may, if desired, be applied as a conversion mechanism to an existing tractor equipped with the Ferguson System load responsive automatic power lift control. Moreover, the mechanism has been shown as incorporated in a crane since it has a special utility in such a device and because certain aspects of the invention involve the crane directly. It should be understood, however, that the present invention is not, in its broader aspects, limited either to appliances for the illustrated tractor with Ferguson System alone, nor to use simply with cranes as distinguished from other implements or the like. On the contrary, the intention is to cover alternative applications, embodiments and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to the first embodiment of the invention herein illustrated (Figs. 1 to 8), those skilled in the art will readily recognize the tractor 28 (Figs. 1 and 2) as the familiar commercial tractor with Ferguson System. Such a tractor has a power lift device, together with a load-responsive type of automatic control and for further detail of which reference may be made to U. S. Patent No. 2,118,180 previously identified. For the present sufi'ice it to note that the power lift device is here shown (see Fig. 2) as embodying a hydraulic actuator 2 I, in this instance a one-way ram comprising a cylinder 22 and a piston 23. Pressure fluid, such as oil, is supplied to the cylinder 22 by a pump 24 powered from the tractor engine (not shown). The dispatch of pressure fluid to the cylinder, and exhaust of same from the cylinder, is controlled by a slidable main valve, the stem of which is indicated at 25. The valve has a central neutral position from which it may be moved (to the left in Fig. 2) to a fluid-supply position or (to the right) to an exhaust position. As the piston 23 moves outward it operates, through a depending arm 26, to raise a pair of crank arms 21. A pair of laterally spaced lower draft links 28 are suspended from these crank arms by drop links 29, the draft link being freely pivoted at their forward ends at points located beneath and slightly forward of the rear axle 38 for the tractor. Exhaust of fluid from the cylinder 22 permits the crank arms 21 and attached draft links 28 to descend by gravity.

Raising and lowering of the draft links 28 between their extreme upper and lower positions is normally accomplished in the Ferguson System by a manual control lever or quadrant lever 3| (Fig. 2). This lever has rigid with it an cecentric 32 which bears against the upper end of a floating lever 33. The lower end of this floating lever is forked (not shown) to engage between bosses on the end of the slidable main control valve and it is urged in a clockwise direction (as viewed in Fig. 2) by a tension spring 34. When the quadrant lever is pushed down toward its lowermost position the floating lever is rocked about an intermediate point 35 by the eccentric 32 to move the main valve into an exhaust position in which fluid is bled from the cylinder 22. On the other hand, when the quadrant lever is pulled upward to its full upper position the eccentric 32 permits the floating lever 33 to be rocked about the point 35 by the pull of spring 34 to move the main valve into fluid supply position and in which pressure fluid is dispatched to the cylinder 22. When the piston 23 completes its resultant stroke of outward travel the outer end of the piston engages the floating lever and restores it to a neutral position in which the fluid is locked in the cylinder behind the piston.

Provision is also commonly made in the Ferguson System for automatically shifting the main valve in response to changes in draft load on an implement borne by the draft links 28 so as to maintain constancy of such load. For that purpose a control rod 36 is mounted for endwise sliding movement and is connected by a yoke or link 31 with the intermediate point 35 on the floating lever. The outer end of this rod is pivoted at 38 (see Fig. 4) to the apex of a bell crank or shackle 39 pivoted on a. long pin 40 at the upper rear portion of the tractor; and a heavy compression spring 4| is arranged to resist forward movement of the rod 36. A forward thrust is applied to the rod 36 which is proportional to the draft load on the implement, this application normally being efiected by means of a top link such as shown in Patent 2,118,180 referred to above and which is pivoted by a pin 39a. to the rearwardly projecting upper end of the shackle 39 to rock the latter forward.

The extent to which the upper end of the floating lever 33 is moved by eccentric 32 will determine the extent of inward movement of control rod 36 required to place the main valve 25 in its neutral position. Consequently, control of the system through the control rod is effected by the application of a force on the rod suflicient to move it against the force of the control spring the distance (determined by the quadrant lever setting) required to restore the main valve to neutral. Once a particular setting has been made, a movement of the quadrant lever necessitates a corresponding movement of the control rod to reestablish equilibrium of the system with the main valve at neutral. Similarly, in the automatic operation of the system as disclosed in the aforesaid Ferguson patent, a movement of the control rod by a variation of the force applied thereto by a change in the draft load will cause a corrective movement of the main valve to admit or exhaust fluid from the cylinder to lift or lower the links 28 and lessen or increase the draft load and the force exerted on the control rod. As before, the system is restored to equilibrium when the valve is returned to neutral, this time by movement of the control rod.

Stated in another way, the requirements for draft control in the system above described make it impractical to effectively maintain the draft links and attached implement intermediate the upper-and lower limit positions of the links under control of the quadrant lever alone. If the quad-- rant lever is moved to a point intermediate its limit positions it will shift the control valve from neutral position either to the exhaust or the fluid supply position, depending upon the force acting through the top link, and consequently the draft links will be lowered or raised until they reach a limit position. Upon shifting of the control valve to'exhaust position, whether by a slight or a large movement of the quadrant lever, lowering of the draft links proceeds until they reach their lower limit position with the attached implement in contact with the ground. Thereafter, of course, ground reaction on the implement may actuate the control valve to effeet a raising or lowering of the links through a relatively small distance, but such movements are confined to a range adjacent the lower limit position in which the implement is at all times in contact with the ground. Conversely, upon movement of; the quadrant lever to'shift the control valve into fluidsupply position, the lift mechanism swings the draft links upwardly to their upper limit position.

It will be appreciated from the foregoing brief description of the typical action of a load-responsive control such as is employed in the FergusonSystem that the main valve is not positively held in its neutral position. Consequently, while it is possible to position the valve at neutral by manipulation of the quadrant lever, other factors may disturb the equilibrium thus established, Hence, the control solely by the operator of the position of the lower links and of an implement or other load carried by them throughout the intermediate range of link movement is an impositive rather than a positive control.

Pursuant to the aims of the present invention provision is made in the illustrated apparatus for making positive the operators control of the system by rendering the controls positionresponsive rather than load-responsive. More particularly the controls causethe piston to follow with fidelity all movements of the quadrant lever 3|. For that purpose the arrangement is, in brief, such as to translate movement or thrust of some member, which is movable in unison with the piston 23, intoa displacement of the control rod 36- and in a direction to move the piston correctively, whenever required, to retain it continuously at a control point determined by the quadrant lever 3!. By control point is meant the point in the pistons range of move ment which corresponds precisely to the point occupied at the moment by the quadrant lever in its range of movement, and at which the piston will be stopped by the return of the main valve to neutral as the piston moves to such point. In other words, the arrangement is such that upon movement of the quadrant lever from one position to another intermediate its limit positions, the draft links will be raised or lowered to a corresponding position intermediate their upper and lower limit positions. Moreover, the links will be held in such intermediate position until the quadrant lever is again shifted.

Inthe particular arrangement shown in Figs. 1 to 8 an auxiliary member herein shown as a cam follower roller 42 is arranged to be swung generally vertically in unison with the traveling motion of the piston 23, and this roller rides along a camtrack formed by the rear edge of a lever or auxiliary Iink'43, the latter serving; in con junction with the spring 4|, to displacelthei-control rod 36 in an endwise direction. Consider ing these parts somewhat more in detail. (see: Fig. 4) it will be observed that the lever 43 1s: pivoted to the outer end ofthe shackle39, being: arranged to depend freely from the. same and having its lower end or tail portion fulcrum'edagainst the underlying outer face of the: difier ential' housing at the rear end of the: tractor; The cam follower roller 42', on theother handpis carried by an elongated upper link or link assembly 44', pivoted at its forward end onthe transverse pin 40 on the differential housing so that the link can swing vertically about this pin. The trailing end of the link 44 is pivoted" (see Figs. 1 to 2) at 45 to a pair of upwardly converging struts 46 mounted at their lower ends on pins 41a extending endwise from a transverseba-r 41. The latter is detachably connected with the draft links 28 through these same pins 41aen-' gaging suitable universal ball joints on the trail ing ends of the links.

As the draft links 28 swing upward in response to rearward movement of the piston 23 the upper link 44 is correspondingly swung upward and the roller 42 rides along the cam track onthe lever 43. The cam track is carefully developed so that the roller will, asit' rises, permit lever 43 to be rocked outward under the urging of thespring 4i thus moving the control rod 36 outwardly. Similarly upon the descent of the draft links 28, the roller 42 rides downward along the lever 43 gradually rocking the latter forward, compressing the spring 4| and shifting the control rod 36 inwardly;

The shape ofthe cam track constituted by the rear edge of the lever 43 is developed sothat a proper increment of the control rod move-- ment will be obtained for each comparable increment of roller movement along the length of the cam track surface. By suitable shaping of the cam track on the lever 43 a full stroke of movement'for the control rod 36 can be imparted to the latter during any desired portion of the" range ofswing for-the draft-links- 2-3: This can. be done while still maintaining a strict propor tionality between movement of the control: rod and shift of the quadrant lever 3 able, however, that substantially thefull range of swing of the draft links 28 be utilized in efiecting the full range of displacement for the the. piston, the quadrant lever and the piston.

are so correlated that the position; of" the former" will fix the position to which the latter must move and stop.

Assuming the mechanism to. be in its; fully lowered position shown in Fig. 2, the cam track" on the lever 43 is in the. present instance such that; the control rod 36 is thrust: inward the maximum distance possible for the same. In suchcase a head 48on therod 36 has aclearance indicated at c. from the inner face of the housing.

To raise the draft links 28 the operator has only to move the quadrant lever 3 l in an upward direction. The draft links will thereupon moveupward',- following previsely the movement of the It i'S" desir- 1 acaasas quadrant lever. For examplalf the quadrant lever is moved upward from its lowermost position through half its range of travel the eccentric 32 will be correspondingly turned, thereby permitting the floating lever 33 under the influence of spring 34 to rock about the point 35 to shift the main valve 25 from the exhaust position it normally occupies at lowest quadrant lever position to its fluid-supply position. Thereupon additional pressure fluid is supplied to the cylinder 22 behind the piston 23, forcing the latter outward with a resultant raising of the lower draft links 28. Accordingly, the roller 42 moves upward along the cam track on the lever 43 and gradually relaxes its thrust and hence the compression of the spring 4|, permitting the control rod 36 to slide outward. This outward motion of the control rod tends to rock the floating lever 33 rearward (clockwise as shown in Fig. 2) in a direction to close the main valve and cut off further supply of pressure fluid. When the piston 23 reaches its control point, as established by the position to which the quadrant lever 31 has been moved, the outward movement of the control rod 36 will be just sufficient to close the main valve and thus retain the mechanism in equilibrium with the draft links 26 raised a distance proportional to the displacement of the quadrant lever 3! in the latters range of travel.

Should there be any inadvertent disturbance of the equilibrium condition noted above, as for example, by leakage of fluid, the system will operate automatically to restore the equilibrium condition. Thus should the draft links 28 lower slightly the movement of the roller 42 down the lever 43 will force the control rod 36 to move inward slightly, thereby opening the main valve for admission of additional pressure fluid to restore the piston 23 to its control point. And, as before, when the piston reaches its control point the main valve is returned automatically to neutral.

Any subsequent shift of the quadrant lever 3| establishes a new control point and the system operates automatically in the general manner described to shift the piston 23 to the new control point, bringing the mechanism to equilibrium condition upon its arrival at such point. In this way the draft links 28 are caused to follow accurately the movement of the quadrant or hand control lever 3| throughout their entire range of movement.

Attention may now be turned to the particular form of upper link assembly herein illustrated (see Figs. 6 and 7). This assembly 44 includes in the present instance a pair of bars 49 apertured at their forward ends to receive the elongated transverse pivot pin 40.

The particular mounting here shown for the shackle 39 is a special one disclosed in my pending application Serial No. 626,395, filed November 2, 1945, now Patent No. 2,486,257. It will be apparent to those skilled in the art, however, that only a minor dimensional change is required for the upper link assembly 44 to accommodate it to the standard mounting provided as a part of the Ferguson System tractor.

The bars 49 converge toward each other at their trailing ends. Upper and lower straps 50 span the forward portions of the bars 49 and are welded to them. Longitudinally spaced bolts and 52 extend between the side bars 49 at points located rearwardly of the straps 50. The bolt 5|, as will become apparent, forms the base of the supporting means, in this instance a pair of bars 53, which holds the roller 42 operatively associated with the cam 43, the bolt being received in longitudinal notches 55 in the bars 53 to enable fore and aft adjustment of the roller position. Preferably bushing 56 is sleeved over the bolt to serve as a spacer for the bars 49.

The follower roller 42 is mounted for movement into and out of a position for active engagement with the cam track on the lever 43 in order to facilitate ease of attachment and detachment of the upper link assembly 44. For that purpose the roller 42 is journaled between the forward ends of a pair of the bars 53 (Fig. '7) which are slidably received between the pair of straps 50 and are guided for endwise sliding movement by a bolt 54 extending vertically between these straps. The rear ends of the bars 53 are notched as noted above to receive the bushing 56 on transverse bolt 5|.

To look the roller supporting bars 53 releas ably in their forward position, a toggle mechanism is utilized. Such toggle comprises a pair of links 51 and 58 pivoted together at 59. The forward end of the toggle link 51 is pivoted on a bolt 60 extending between the pair of slide bars 53, whereas the opposite end of the other toggle link is pivotally supported by the bushing 56. A transverse stop and handgrip pin 6! is welded to the upper side of the toggle link 58 to engage the bars 53 and thus limit the downward movement of the toggle to a slightly over center position. With the toggle in its extended position as shown in Fig. '7 the roller supporting bars 53 are held thrust forward so that the roller 42 is positioned for contact with the cam track on the lever 43. To release the roller from engagement with the cam track it is necessary merely to grasp the pin 6! and pull upward, whereupon the toggle is broken upward over center to the angular dotted line position shown in Fig. 6 and in which the roller is withdrawn. This position provides ample clearance between the cam and roller for the operations of assembly, disassembly and adjustment.

A crane is typical of those implements which can most readily be manipulated by a positionresponsive type of control as contrasted with, say, a plow with which it is desirable to use a load-responsive control. The particular crane which is shown in Figs. 1 to 5 as mounted on the draft links 28 is of a novel type, specially coordinated with the control mechanism illustrated, so as to accomplish substantially equal increments of vertical motion for the active outer end of the crane boom for each corresponding increment of movement of the quadrant or hand control lever 3|.

The particula crane illustrated includes a. rearwardly projecting boom 62 with a pair of reinforcing trusses 63. An intermediate portion of the boom is cradled in a depending U-shaped yoke 64 carried by transverse pivot pin 65 over which the trusses extend. The pivot pin 65 is carried by the upper ends of two pairs of supporting legs 66 and 6?. The lower ends of the pair of legs 66 are apertured to receive the pin projections on the ends of the horizontal bar 47, thus pivoting them to the trailing ends of the draft links 26. The lower ends of the other pair of legs 61 are apertured to receive the transverse pin 45 which pivotally connects them to the trailing end of the upper link assembly 44 and to the struts 45.

An adjustably extensible connecting link, designated generally as 68 ,is pivotally connected to extend between the forward or butt end of the boom -I52 and an intermediate point on the upper link assembly M. In the particular construction shown (Fig, 2) this extensible link 68 includes a tubular member 69 having a nut 70 welded in its upper end and in which is threaded a rod H. At vthe upper end of the connecting link the threaded rod H is fixed to a U-shaped yoke Ha which is pivoted to the flattened forward end of the boom 62. Spokes 12 project radially from the tube 69 to facilitate turning of the same and thus thread the nut .10 along the rod 1! to vary the length of the connecting link. At the lower end of the connecting link the tubular member 69 has .a suitable universal connection 13 with the pin .52. ,As .shown in Figs. 6to 8, inclusive, the connection comprises a pin 73a welded to a collar 13b which in turn is welded in the end of the member 69. The-outer end of the pin has a head 73c-which seats against the flat face of a semicylindrical rocking member 13d arranged with its cylindrical face engaging the complemental inner surface on the base of a yoke 74. The latter is ,pivotally mounted on a bushing 15 on the transyerse bolt .52 in theupper link assembly 44. The pin 13a extends through an elongated slot Ma the base of the yoke '54 to permit of relative rocking movement of the parts.

By adjusting the length of the connectin link 68 the inclination of the boom .62 with reference to the horizontal, when the draft links 28 are in the fully lowered position shown in Fig. 2, may bealtered at will.

A comparison of Figs. 2 .and 3 will reveal the fact that the arrangement is such that there are, in effect, two quadrilateral linkage figures which are alternatively distended and collapsed as the crane is raised and lowered. It is this opposite collapsing and extending movement of the two quadrilateral linkage figures which is utilized to cause the active outer end of the boom to rise in substantially a straight vertical line and at substantially a constant rate. The lower one of the two quadrilateral linkage figures is constituted at its upper and lower ,sides'by the upper link assembly 44 and the lower draft links 28, the figure being completed at the rear end by the struts 46 and at the front end by the rear portion of the tractor. In the other or upper quadrilateral linkage figure, on the other hand, the connecting link 68 and supporting legs '67 form the forward and rearsides of the figure, the same bein completed at'its upper end by the intervening portion of the boom .62 and at its lower end by the trailing portion of the upper link assembly 44. As the crane is raised from the position of Fig. 42 to that of 'Fig. 3 the lower quadrilateral linkage figure collapses and the upper figure distends, Whereas whenthe crane descends the'lower figure distends and the upper figure collapses.

The collapse of the lower linkage figure and simultaneous distention of the upper linkage figure, as the boom rises, causes the outer end of ,the'boom to move ire-arwardly, with reference "to the draft links 28, simultaneously with its rise and by proper development of the pivot point relationship of the linkage the outer end ,of the boom can be made to follow a substantially Itrue vertical path. The path is not precisely a truly vertical one but is suiiiciently closefor practical purposes.

.It is important to note, moreover, that the components, .of the :two quadrilateral linkage figl ures described above are related so that for any 10 given unit increment of piston travel in the main cylinder 22 the outer end of the boom 62 travel vertically an incremental distance which bears a fixed proportionality to the piston travel throughout the entire range of movement. In that way itis insured that the lifting force available at the end of the boom will be substantially uniform throughout the upward travel of the boom, a highly desirable feature which has been lacking in tractor borne cranes heretofore available.

The special form of the load hook '16 fixed to the outer end of the boom 62 should be noted. Instead of the usual deep hook this hook 16 is very shallow and has no keeper .or extra bend at its outer end. That special form of hook greatly increases safety of operation, since it minimizes the danger of up-ending the tractor when going up an incline with a load borne by the crane. If the operator tries to drive the tractor up a slight incline when the crane is carrying a load, the upward tipping .of the tractor shortens the moment arm between the front and rear axles while correspondingly increasing the moment arm of the load on the rear axle. 'I'hat change in moment arms may be enough to overbalance the tractor and cause its front end to rear up. With the shallow form of hook shown and if the tractor should tie up a sufficient distance to ground the load, the hook will readily pull free of the grounded load. And once the tractor is relieved of load the front wheels will immediatelydrop back to the ground.

In further reference to safety of operation, it is to be observed that the position-responsive type of control here afforded greatly enhances safety of crane operation. In contrast, if a crane is used with a tractor power lift having simply a load-responsive control land with which the crane must always be elevated to full height for transport, theload is often carried at a dangerous height from the ground. In the present installation, on the other hand, the load need be lifted only far enough to clear the ground during transport, and no higher, thereby resulting in a much more stable condition.

The operationof the mechanism shown in Figs. -1 to 8 will ingeneral be clear from the foregoing. By way of brief recapitulationlet us assume that the crane is in the lowered position shown in Fig. 2. In such case the operator backs up the tractor to a load and throws the sling or the like (not :shown) from the load over the hook [6. Then he pulls the quadrant lever 3| upward and as he does so the crane rises to'a position corresponding to the location of the quadrant lever and lifting the load. It will be understood that if the lever 3| :is moved quickly the piston, and parts borne by it, may lag behindbut will quickly catch up .to the lever once it is put in its new position. .Once the load is sufficiently clear of the ground the operator simply lets thequadrant lever stay where it is and drives the tractor to the unloading point. As heretofore noted, the load is lifted substantially straight upward by the crane and with a uniform application of force during the rising movement. Moreover, the'ci'ane follows accurately the motion of the quadrant lever in all positions of the latter and isautomatically retained in any position dictated by the location of the quadrant lever quite irrespective of variations in load, etc. It is also to be observed that vibration and jarring incident to movement of :the tractor does not cause ,the

roller 42 to jig le the control rod 36, therebydisl1 turbing the equilibrium condition in the hydraulic system. Any such disturbance is avoided in that the upper link assembly 44 is pivoted directly to the tractor by the pin 40.

Installation or removal of the mechanism for converting the controls to a position-responsive type is a simple matter. The entire applied mechanism shown can be detached simply by disconnecting the pins 4'! from the ball joints at the trailing ends of the draft links 28 and removing the pin40 at the forward end of the upper link assembly 44. The roller 42 should be at the upper end of the cam track on the lever 43 before its toggle 51-58 is broken to withdraw the roller so that the main spring 4| will not be under compression at that time. The lever 43 can, of course, be readily unpinned from the shackle 39. Changeover from a load-responsive system to a position-responsive system, or vice versa, is thus a very simple matter.

In Figs. 9 to 11 is shown a modified form of mechanism also embodying the present invention. The crane structure is identical with that of Figs. 1 to 8. In fact, the entire arrangement differs simply in that a linkage type of mechanism has been used for applying thrust to the control rod 36 rather than the cam and roller set up previously described. Accordingly, the same reference numerals have been applied to identical parts and only the changed portions of the mechanism need be described.

In the installation of Fig. 9, thrust is applied to the control rod 38 by an adjustably extensible thrust link or auxiliary link I comprising a tubular member l0! having a nut I02 fixed in its rear end and in which is threaded a rod I03. A swivel joint I04 at the forward end of the tubular member |0l connects the same to a jaw I05 having a shield I06. The jaw partially embraces and bears against the pin 3911 at the upper rear end of the shackle 39. This arrangement facilitates adjustment as well as assembly and disassembly. Thus to disassemble, the jaw is retracted by properly rotating the tubular member until the jaw can be swung free of the pin 39a. In reassembly the retracted jaw is swung into alignment with the pin where it is held by the shield until the jaw has been advanced just the distance necessary to take up the slack or play in the assembly, preferably without moving the control rod inwardly.

At its trailing end the adjustable thrust link I00 is pivoted at to the upper end of an intermediate lever or link [03 defining, in this instance, the auxiliary thrust-applying member. The latter lever is pivoted intermediate its ends at I09 between a pair of side bars H0 constituting an upper link 44a corresponding to the link 44 of the installation of Fig. 1. The lower end of this intermediate lever I08 is pivoted at III to the forward end of a link H2 which is, in turn, constituted by a pair of bars (see Fig. 10) pivoted at their trailing ends by a collar H3 on a bar I41 extending between the trailing ends of the draft links 28 and corresponding to the bar 41 of the modification first described.

The links I00, I08 and H2 thus constitute an extensible Z-shaped linkage which is collapsed and distended as the lower draft links 28 are correspondingly raised and lowered. The collapsed position is shown in full lines in Fig. 9 and the distended position is indicated in broken lines in the same figure. As the Z linkage collapses the pressure on the spring 4| is gradually relaxed, permitting the control rod 36 to slide outward. And as the linkage distends the control rod is gradually moved inward. Adjustment of the length of the thrust link I00 serves as a simple and ready means for coordinating the travel of the control rod with that of the quadrant lever. The Z linkage is of course developed as to its pivotal relations to produce the same movement of the control rod 36 as was obtained by the action of the cam following roller 42 on cam 43. Thus any movement of the control quadrant lever by the operator will shift the control valve to an intake or exhaust position as the case may be to produce a corresponding movement of the piston 23 and consequently of the lower links, which in turn results (through operation of the Z linkage) in a corresponding travel of the control rod until the valve is returned to neutral. Thus the control position as designated by the quadrant lever is reached. This position once reached is maintained until the operator changes it by again shifting the quadrant lever.

I claim as my invention:

1. The combination of a tractor having thereon a hydraulic power lift including an actuator, a hand lever together with a movable control member yieldably biased toward one extremity of its path of travel for conjointly controlling the operation of said actuator. and a pair of positively acting elements defining a thrust transmitting connection between said power lift and said movable control member for progressively displacing said control member against the action of its bias in proportion to movement of said actuator inv one direction and for freeing said member for return movement under the urging of its bias progressively in proportion to movement of said actuator in the opposite direction.

2. A conversion attachment for converting a load-responsive type of automatic control for a power lift device on a tractor to a position-responsive type of control and in which the loadresponsive type of control includes a stressresponsive device having a member pivoted on the tractor for correctively returning the power lift device to a predetermined control point upon change in stress of said control device from a predetermined value, said attachment comprising a stress applicator attachable to the stressresponsive device for stressing the latter by bodily shift of said applicator, and an element connected with said power lift device for movement in unison therewith, said element being disposed between said power lift device and said stress applicator for subjecting the latter to displacement in rigidly controlled proportionality with respect to changes in position on the lift device.

3. For use on a tractor having a pair of draft links trailingly pivoted on the differential housing for elevation by a power lift device and having a load-responsive type of automatic control including a spring-urged slidable control rod with a shackle at its outer end, a conversion attachment for use in converting the same to a position-responsive type of control, said conversion attachment comprising: a lever adapted to be ivoted at its upper end to said shackle with the lower portion of the lever fulcrumed on the differential housing, an upper link adapted for pivoting on the differential housing above the draft links for vertical swing, means for swinging said upper link in unison with the vertical swing of said draft links, and means including a cam surface and a cam follower interposed between said tachment for use in converting the same to a 13 top link and said leverto effect aprogressiveion ward rocking movement of said lever as said draft lin ks descend so that a progressive displacement of said control rod occurs in response to vertical swing of said draft links.

4. For use on a tractor having a pair of .draft 'links'trailingly pivoted on the diiferentialhousi'ng thereof for elevation by a power lift :device and having a load-responsive type of automatic control including a spring-urged slidable control rod with a shackle at its outer end, a, conversion attachment for use in converting the same to a position-responsive type of control, said conversion attachment including: alever adapted to be dependingly pivoted to the shackle-with the lower "tail of said lever fulcrumed on the differential housing, said lever presenting a-cam 'trackon its rear edge, an upper link adapted to be pivoted on the differential housing above the draft link to swing vertically, said upper link'having a roller in position to ride along said cam track, means for rocking said upper link in unison with the vertical swing of said draft links, and said cam track being developedto afforda progressive forward rocking of said 'lever'by said roller as said draft-links descend, to thereby effect a progressive displacement of said control rod in response to vertical swing of said draft links.

5. For use on 'a tractor having a pair of draft links trail'ing ly pivoted on the differential housing for elevation by apower lift device and having a load-responsive type of automatic control including a spring-"urged slidable control rod with a shackle at its outer-end, a conversion at- -position-responsive type of control, said conversion attachmentincluding an upper link pivoted on the rear of the tractor above the draft links toswing verticallymeans for rocking said upper link vertically in unison with vertical swing of said lower draft linksyand a Z linkage arranged with-the central leg of the Z pivoted intermediate its ends on said upper link to rock fore and aft thereon, the trailing end of the lower leg of the 2 being pivotally connected to the lower draft links and the forward end-of the upper leg of the 2 being pivoted to the shack-l e at the outer end of the spring-urged control rod on the tractor foreffecting'endwise displacing of suchcontrol rod in response to vertical swinging movementof said lower draft links.

6. The combination of a tractor having a power lift device thereon operative to swing vertieally atrailing draft link on the tractor, a load member for projection upwardly and rearwardly from thetractor rear end, a manual control mem- "ber on said tractor, automatic control means for eflecting a follow-up action of said power lift device with reference to said control member as the latter is moved, and linkage supporting-said load member on said link for effecting vertical movement of the outer end of the load member in uniform proportionality with respect to displacement of said control member.

'7. The combination of a tractor having a power lift device thereon operative to swing vertically .a trailing draft link in the tractor, a load :member for projection upwardly and rearwardly from the tractor rear .end, a manual control member on the tractor, and linkage supporting said .load member on said link'for effecting vertical movement of the :outerend of said load member :in uniform proportionality with respect to dis- ;plac'ernentof said control member.

18.15. crane attachment for a tractor having a draft link trailing-1y pivoted .oniits \rearend portion for vertical swinging movement bya power lift device on the tractor, said attachment comprising a load member having a free outer end to extend upwardly and rearwardly from the tractor rear end, and linkage for supportingly attaching said load member to said draft link'as well iasfor imparting to the load member a vertical movement of its outer end in uniform proportionality to movement of said power lift device.

9. A crane attachment for a tractor having a pair of draft links trailingly pivoted in spaced side-by-side relation from its .rear end portion for vertical movement by a power lift device on the tractor, said attachment comprising an upper .link adapted to be trailingly pivoted gen- .erally centrally from therear .of the tractor and above the draft links, strut meansfor pivotally connecting the trailing end of said upper link to the trailing ends of said draft links, a crane boom, first and second pairs of generally upright supporting legs rising from the rear portion of said upper link and from the rear ends of the draft links, respectively, and pivoted thereto to rock fore and aft, means pivoting an intermediate portion of said boom to the upper ends of both of said'pairs of legs with said boom lying generally horizontal and projecting rearwardly, and means including aconnecting link pivotally connected to the forward end of said boom and to an intermediate portion of said upper link for rocking said pairs of legs fore and aft to thereby move said boom endwise as the draft links raise and lower it bodily.

10. A crane attachment for a tractor having a draft link trailingly pivoted on its .rearend portion for vertical swinging movement by :a power lift device on the tractor, said attachment comprisin upper and rear linkage means pivoted to each other and adapted to be pivoted respectively to the rear portion of the tractor and to the draft link to complete therewith a first quadrilateral linkage figure which collapses as the draft link rises and distends as such link descends, .a generally horizontal crane boom, and generally upright links connected to the boom at spaced points and to said upper link at spaced points to complete therewith a second quadrilateral linkage figure and which collapses as the draft link descends and distendsas thedraft link .rises.

11. A crane attachment fora tractor having a draft linktrail'ingly pivot-ed -:on ritsirear end por- 'tion for vertical swinging movement by .a'power lift device on the tractor, said attachment vcomprising a generally horizontal crane boom, and .linkagemeans conncctable between the boom and draft link for effecting a substantially true vertical motion of the outer end of said boom upon vertical swing of said links, said linkage means being arranged :in two linkage figures which alternately collapse and distend as the draft link swings vertically up and down.

12. For use on a tractor having a draft link trailingly pivoted thereon for elevation by a power lift device and having a load-responsive type of automatic control including a spring biased control element tinwhich movement against the force of bias causes raising of the draft link, a conversion attachment for converting said control into a position-responsive type of control comprising: an elongate auxiliary link having a first portion .and a :second portion, said first portionrbeing adapted'for attachment to said spring biased control element for moving the-.-.same,said

second portion being remote from said first portion and providing a thrust receiving means, and an auxiliary member interposed between the draft link and said second portion of said auxiliary link and engaged with the latter for the application of thrust thereto incident to downward swinging movement of the draft link whereby said auxiliary link subjects said control element to corresponding movement against its force of bias.

13. For use on a tractor having a draft link trailingly pivoted thereon for elevation by a power lift device and having a load-responsive type of automatic control including an axially movable control rod and a shackle pivoted thereto in which inward movement of the shackle causes raising of the draft link, a conversion attachment for'converting said control into a positionresponsive type of control comprising: an auxiliary link, said auxiliary link having a first portion adapted for pivotal connection to said shackle and having a second portion remote therefrom, means associated with said second portion for mounting said auxiliary link for inward and outward shackle movement, and means operatively interconnecting the draft link with the auxiliary link so that upon vertical swinging movement of the draft link said auxiliary link imparts to said control element movement which is in strict proportionality with the swing of the draft link.

14. For use on a tractor having a draft link trailingly pivoted thereon for elevation by a power lift device and having a load-responsive type of automatic control including a spring-urged slidable control rod in which movement in one direction from a neutral position causes raising of the draft link and movement in the other direction causes lowering of the draft link, a conversion attachment for converting said load-responsive control into a position-responsive type of control comprising, in combination: a top link having provision at its forward end for pivoting to the tractor adjacent the control rod, means for interconnecting said draft link with said top link so that said links swing vertically in unison with one another, an auxiliary position-control link having a first portion arranged for coupling to said control rod and having a second portion remote therefrom and so mounted as to enable inward and outward movement thereof to be transmitted to said control rod by said link, and a member operatively interconecting said auxiliary top link with the auxiliary link so that upon downward swinging movement of the top link there is effected simultaneous movement of the control rod against its spring.

15. For use on a tractor having a draft link trailingly pivoted thereon for elevation by an hydraulic power lift device and having a valve for controlling said power lift device which is jointly under the control of a manual lever and a control rod spring-urged against the force imposed by a load on the draft link in which movement of the rod under load in one direction from a neutral position determined by said lever causes raising of the draft link and movement in the other direction causes lowering of the draft link, a conversion attachment for convertin said load responsive control into a position-responsive type of control comprising, in combination: a top link having provision at its forward end for pivoting to the tractor adjacent said control rod, means for interconnecting said draft link with said top link so that said links swing vertically in unison with one another, an auxiliary position-control link having a first portion arranged for coupling to said control rod and having a second portion remote therefrom and so mounted as to enable inward and outward movement thereof to be transmitted to said control rod by said auxiliary link, and a member operatively interconnecting the top link with the auxiliary link so that upon upward swinging movement of said links caused by repositioning of said manual lever there is effected corresponding movement of the control rod to shift said valve to a neutral position.

16. In a tractor, the combination comprising a draft link trailingly pivoted on its rear end portion for vertical swinging movement; an hydraulic power lift device including a valve for controlling the same; a manual control lever and a spring biased control element in which movement under load against the force of bias from a neutral position determined by said manual lever causes raising of the draft link; means for converting said control alternatively into a position-responsive type of control comprising an auxiliary link having a first portion and a second portion, said first portion being attached to said spring biased control element for moving the same, said second portion providing a fulcrum for fore-and-aft rocking of the auxiliary link, and a member operatively interconnecting the draft link with the second portion of said auxiliary link and disposed for the application to the latter and said control element of rocking movement which is proportional to the vertical swinging movement of the draft link.

17. A tractor having, in combination, a pair of draft links trailingly pivoted thereon, a hydraulic ram operatively associated with the draft links, a control system for said ram comprising valve means shiftable in opposite directions from a neutral position to control the supply of pressure fluid to and exhaust of pressure fluid from said ram to effect a raising or lowering of the draft links, a manually positionable quadrant lever, a valve lever having at one end a position; ing connection with said shiftable valve means, means providing a fulcrum for said valve lever intermediate its ends, said valve lever having its other end in engagement with said quadrant lever whereby the valve lever may be rocked on said fulcrum to shift said valve means to effect raising or lowering of the draft links, and characterized by having means including coacting cam and follower elements for shifting said fulcrum in a direction to effect return of said valve means to neutral position as the draft links reach a position corresponding to that of the quadrant lever, one of said elements being displaceable in unison with the raising and lowering of said draft links and the other of said elements reacting to such displacement to shift said fulcrum.

18. A tractor having, in combination, a pair of draft links trailingly pivoted thereon, a hydraulic ram operatively associated with the draft links, a control system for said ram comprising valve means shiftable in opposite directions from a neutral position to control the supply of pressure fluid to and exhaust of pressure fluid from said ram, said ram raising said draft links upon admission of pressure fluid thereto and lowering the draft links upon exhaust of pressure fluid therefrom, a manually positionable quadrant lever, a valve lever having at one end a positioning connection with said valve member, a shiftable plunger in engagement with said valve lever intermediate its ends, said valve lever having its other end in engagement with a part associated 17 with said quadrant lever, said quadrant lever being operative through said part to rock said valve lever about said plunger as a fulcrum and thereby shift said valve means so as to efiect raising or lowering of the draft links, and characterized by having means including coacting cam and follower elements operative to rock the valve lever about said quadrant lever part as a fulcrum and in a direction to effect return of said valve means to neutral position as the draft links approach a position within their range of movement corresponding to that of the quadrant lever within its range of movement, one of said elements being displaceable in unison with the raising and lowering of said draft links and the other of said elements reacting to such displacement to rock said valve lever.

, 19. The combination with a tractor having a pair of draft links trailing-1y pivoted thereon, power lift means including a hydraulic ram for raising and lowering said draft links, and a control mechanism of the draft responsive type for said ram comprising valve means controlling the supply of fluid to and exhaust of fluid from the ram, a valve shifting lever, a quadrant lever providing a variable fulcrum for one end of said lever, means including a spring biased plunger adapted to be displaced in proportion to changes in the external force exerted thereon and operative upon such displacement to swin said lever on its fulcrum, said lever being operative to actuate said valve means and initiate a raising or lowering of the draft links by said ram to reestablish a predetermined external force on said plunger as determined by the setting of said quadrant lever; means for converting said draft responsive control to position responsive control in which the draft links are moved to and held in a position corresponding to the position in which said quadrant lever is set, said converting means comprising a member pivoted on the tractor and operative when rocked about its pivot to swing said valve lever on its fulcrum, and a member movable in unison with the draft links in their raising and lowering movements cooperating with said pivoted member to rock the same about its Divot and position the links in conformity with the position of said quadrant lever.

20. A tractor having, in combination, a pair of draft links trailing-1y pivoted thereon, power lift mechanism including a hydraulic ram for raising and lowering said draft links, control mechanism normally responsive to the draft load on an implement attached to said draft links for controlling the operation of said ram, said mechanism including valve means shiftable in opposite directions from a neutral position to initiate the supply of pressure fluid to or exhaust of pressure fluid from said ram, a valve shifting lever,

a quadrant lever providing a shiftable fulcrum for said valve lever operative to selectively vary the position in which said valve lever returns said valve means to neutral position, said control mechanism being characterized by having means for actuating said valve means through said valve lever to effect the positioning of said draft links at a position within their range of movement corresponding to the position of said quadrant lever within its range of movement, said valve actuating means comprising coacting cam and follower elements one of which is movable in unison with the draft links and the other of which is operatively associated with said valve lever.

21. A tractor having, in combination, a pair of draft links trailingly pivoted thereon, power lift mechanism including a hydraulic ram for raising and lowering said draft links, control mechanism normally responsive to the draft load on an implement attached to said draft links for controlling the operation of said ram, said mechanism includin valve means shiftable in opposite directions from a neutral position to initiate the supply of pressure fluid to or exhaust of pressure fluid from said ram, a valve shifting lever, a quadrant lever providing a shiftable fulcrum for said valve lever operative to selectively vary the position in which said valve lever returns said valve means to neutral position, said control mechanism being characterized by having means for actuating said valve means through said valve lever to effect the positioning of said draft links at a position within their rang-e of movement corresponding to the position of said quadrant lever within its range of movements, said valve actuating means comprising an elongated member operatively connected at one end with said valve lever and adapted to pivot at the other end on the tractor and acting in such pivoting to rock said valve lever, and a member movable in unison with said draft link coacting with said pivoted member to correspondingly rock it about its pivot.

ERNEST V. BUNTING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,367,607 Krieg Feb. 8, 1921 1,511,802 Combs et al. Oct. 14, 1924 1,819,445 Soeflker Aug. 18, 1931 2,118,180 Ferguson May 24, 1938 2,398,585 Hayward Apr. 16, 1946 2,423,485 Court July 8, 1947 2,437,875 Chambers et al Mar. 16, 1948 2,455,727 Bunting Dec. 7, 1948 

